1. Field of the Invention
The present invention relates to network interconnecting devices in general and, in particular, to LAN switches in which the ports are configured to enable communications between the port and attached devices.
2. Prior Art
The interconnection of devices with LAN switches is well known in the prior art. Two types of communications protocols are used to effectuate communications in the network. The Token Ring and ethernet or CSMA/CD (Collision Detect) are the major types of protocol that are well known. The present invention (described below) relates to the Token Ring protocol and further discussion of ethernet or CSMA/CD will not be given.
The details of the Token Ring protocol are set forth in the IEEE 802.5 standard for Local Area Network (LAN) and are incorporated herein by reference. As a consequence, only the portions of the standard that are required to understand the present invention will be given. Historically, Token Ring has a 4 Mbps (Mega bit per second) or 16 Mbps data transmission rate. The protocol for Token ring is usually implemented in a Medium Access Control (MAC) chip which is embedded in a device termed xe2x80x9cadapterxe2x80x9d which interfaces a device or switch port to the transmission mechanism that interconnects the switch port and the device.
In order to simplify system setup and make the switch more user friendly, circuit arrangements, termed xe2x80x9cconfigurorxe2x80x9d, are provided in the ports to reconfigure them so that the communication between ports and attached devices is made possible. Examples of prior art configurors and methods are set forth in U.S. Pat. Nos. 5,625,621 and 5,680,397. Both patents are assigned to the assignee of the present invention and are incorporated herein by reference.
In order to increase the speed and throughput of Token Ring networks, the IEEE 802.5 Amendment 1 has promulgated a 100 Mbps standard. Among the things or requirements set forth in the standard are signal shape and other signal characteristics that are sensitive to impedance changes. To be compatible with the standard, the 100 Mbps must be met with different types of cable, such as Shielded Twisted Pair (STP), Unshielded Twisted Pair (UTP), with different types of resistance (i.e., 150 Ohms or 100 Ohms).
In view of the IEEE 802.5 Amendment 1, there is a need for device to reconfigure high speed port of a Token Ring Switch.
The present invention provides a circuit arrangement (configuror) that configures high speed ports so that signals on the transmit and receive conductors meet the IEEE 802.5 Amendment 1 standard (incorporated herein by reference) without causing signal degradation on both UTP and STP wiring. The circuit arrangement, also, compensates for variations in transmission impedance. A software protocol is then executed as a dialogue between partners (port and attached device) so that both can appropriately auto detect and configure.
The circuit arrangement includes two impedance matching transformers with first and second sets of windings connected to different pins in different connectors located at the high speed port of the switch. A third and fourth Sets of windings are switchable coupled to a switching relay. A controller drives the switching relay so that a capacitor coupled to the primary side of one of the transformer connects the transmit pair to ground potential whether the configuration is in a straight feed through mode or a crossover mode. In the straight feed through mode, signals are received through selected windings of one of the transformers and signals are transmitted through selected windings of the other transformer.
In crossover mode, signals are transmitted via selected windings of said one of the transformer; whereas signals are received via selected ones of the other transformers. The above, as well as additional features and advantages of the present invention, will become apparent.